In recent years, attention has been drawn to scanning-type projectors for displaying an image on a fluorescence screen by scanning the fluorescence screen with a light beam. Such scanning-type projectors often use a galvanometric mirror or a resonant scanning element as a scanning means for scanning the fluorescence screen. Although the resonant scanning element is advantageous in that it can perform high-speed scanning, it is not easy for the resonant scanning element to apply the light beam to an appropriate incident position on the screen because the scanning speed and the scanning amplitude tend to change due to the ambient temperature.
A scanning beam display system that is capable of adjusting the incident position of a light beam on a fluorescence screen is disclosed in Patent document 1.
The fluorescence screen used in the scanning beam display system disclosed in Patent document 1 has a plurality of color stripes arranged in a periodic pattern with servo reference marks, each disposed between adjacent two of the color stripes, for reflecting the light beam.
When the scanning beam display system is in operation, the light beam, which is made up of a plurality of light pulses, is emitted from a light source and applied to the fluorescence screen to scan it in directions perpendicular to the color stripes to excite the fluorescence of each of the color stripes, thereby displaying an image on the fluorescence screen.
The scanning beam display system changes a start-of-emission timing to start emitting the light beam from the light source in each scanning cycle, thereby changing the incident positions of light pulses on the screen in each scanning cycle. When the incident positions of light pulses on the screen change, the amount of light applied to the servo reference marks changes, thereby changing the amplitude of feedback light from servo reference marks. The scanning beam display system detects a change in the amplitude of the feedback light, and adjusts the start-of-emission timing depending on the detected change. In this manner, the incident positions of light pulses on the screen are adjusted to cause the light pulses to be applied to the color stripes.